The attitude of vehicle wheel spindles, commonly known as wheel alignment, is very important to the vehicle's handling and steering characteristics. The down-sizing of automobiles during the last two decades has resulted in the development of more compact and less costly suspension systems. One of these is commonly referred to as the MacPherson Strut and this is a single axis front end (and sometimes also rear end) suspension system consisting essentially of a shock absorber, a coil spring and ball joints, all in a single axis assembly. This strut reacts between a pivotal frame member known as a lower control arm and an upper bracket fixed to the frame or body of the vehicle. This arrangement also eliminates the necessity for what is referred to in some suspension systems as an upper control arm.
While this suspension system has been found to be suitable for certain small sized automobiles, for the most part, it only conveniently permits adjustment of the "toe-in" of the wheel spindle. Toe-in, of course, is the degree to which the wheels point toward one another. It has however, been found difficult to provide any simple arrangement for adjusting the caster or camber angles in the MacPherson Strut suspension. Camber, of course, is the degree to which the wheels lean toward one another--an increase in camber being the degree to which the wheels lean outward from factory specification and a decrease in camber representing a further leaning of the wheels toward one another from specification. The caster angle is the angular pivot of the wheel and wheel spindle assembly about the steering axis of the vehicle--a backward pivot from factory specification being defined as an increase in caster angle and the forward pivot being a decrease in the caster angle.
Attempts have been made to provide the MacPherson Strut with a caster and camber adjustment but because of their cost and complexity, they have been eliminated from the lower priced suspension systems. Moreover, most of these appear to provide only a simultaneous adjustment in caster and camber which is undesirable. For example, the Mattson U.S. Pat. No. 4,026,578 shows a MacPherson Strut assembly capable of simultaneous caster and camber adjustments by the provision of an eccentric at the lower end of the strut assembly adjacent the steering arm. This is an extremely costly assembly and provides only a limited degree of adjustment that also precludes the adjustment of camber and caster independently which is important.
The present invention seeks to ameliorate the problems described above in the prior art.